First-Principles Research on Hard Segment Regulation of Field-Induced Charge Transfer in Polyaniline-Grafted Polyurethane Copolymers

Lightning strikes pose an increasing threat to wind turbine blades, whose insulating GFRP laminates and polyurethane coatings accumulate surface charge with no dissipation pathway. Polyaniline-grafted polyurethane (PANI-PU) copolymers are being explored as conductive coating materials that dissipate charge under high electric fields. This research used density functional theory to compare three graft copolymers differing only in the diisocyanate hard segment, HDI, HMDI and IPDI, under a static field up to 205.7 kV/mm along the backbone with all other conditions identical. The response was analysed by Bader charge partitioning, differential charge density, orbital energetics and surface potential. HMDI-PANI transfers the largest net charge, 0.75 e, keeps its PU hydrogens near neutral at 0.10 e, spreads charge most diffusely with an index of 122.6, and shows the largest gap narrowing, 0.92 eV. HDI-PANI polarizes twelve free C-H bonds, raises its polarizability by 4.0 a.u. while its dipole falls by 0.25 D, and narrows its gap from 2.19 to 1.66 eV. IPDI-PANI reorients its methyl groups, giving the largest polarizability increase, 9.0 a.u., and dipole enhancement, 1.29 D, without a matching gain in transfer, 0.68 e. These results identify the dicyclohexylmethane hard segment as the architecture maximizing transfer efficiency, providing a molecular-level design basis for conductive graft copolymer coatings.